06 2500 truck, runs erratic when you let off the throttle, in gear or not. I noticed the volt meter acting crazy when it does this. I went through some diagnostics, and found that if I unplug the fuel control aqctuator, it runs normally, and the voltage stays steady. So, i replaced the actuator-- no help still does the same. Anyone ever run into this!?

This is a Cummins engine in a GM truck?
This site is mostly for the GM truck Diesel engines and some light Gasser. If Cummins you may search for a Cummins Forum Site to get the best possible help. There are some that know Cummins but I feel you get fast and better help on a site that is more Cummins related.

Brian

The two things that affect voltage when the truck is running are the alternator and the crank sensor. So possibly the crank sensor could be acting up? Its a shot in the dark but it might be something to look at.

Justin

Just so happens that I work at the cummins tech center in columbus IN not that that makes me an expert but I do have accsess to cummins quickserve as well as diagnostic tools and the such. i mostly work with Heavy Duty engines but if I were you the first thing I would do is check ALL grounds!!!! At the battery and the computor grnds on the engine as well as the ground battery cables at the engine. Might not help but first things first.